Put both equations into slope-intercept form, so they look like y = mx + b. Remember than in slope-intercept form, "m" represents the slope of the line.

So, your two equations become:

y = -x + 4

and

y = x + 6.

Thus, the slopes of your two lines are -1 and 1, respectively. (Remember that x really means 1x, and -x really means -1x.)

Now, two lines are perpendicular if and only if their slopes are negative reciprocals of one another. Consider the slope of 1 (the slope of your second line). Think about it as 1/1 (any whole number can be written as a fraction simply by putting it over 1). Now, take the 1/1 slope, make it negative and flip it over. This gives you -1/1, which is the same as -1, which is the slope of your first line. So the slopes of the two lines are negative reciprocals of one another and the lines are therefore perpendicular.

As for #2, maybe you're just restating #1, in which case I think the explanation above should answer your question.